reordered unix targeted documentation to be more user-friendly

Also fixed wrong build root.

docs/build_notes_unix.md

@@ -1,46 +1,60 @@
 Building on Unix systems
 =============================
 
-Common build/install process from sources:
+First of all we need to make sure that all dependencies are satisfied.
 
-* git clone https://github.com/PurpleI2P/i2pd.git
-* mkdir -p 'i2pd/build/tmp' && cd 'i2pd/build/tmp'
-* cmake -DCMAKE_BUILD_TYPE=Release <more options> ..
-* make
-* make install
+This doc is trying to cover:
+* [Debian/Ubuntu](#debianubuntu) (contains packaging instructions)
+* [FreeBSD](#freebsd)
 
-Available cmake options:
+Make sure you have all required dependencies for your system successfully installed.
 
-* CMAKE_BUILD_TYPE -- build profile (Debug/Release)
-* WITH_AESNI -- AES-NI support (ON/OFF)
-* WITH_HARDENING -- enable hardening features (ON/OFF) (gcc only)
-* WITH_BINARY  -- build i2pd itself
-* WITH_LIBRARY -- build libi2pd
-* WITH_STATIC  -- build static versions of library and i2pd binary
-* WITH_UPNP    -- build with UPnP support (requires libupnp)
-* WITH_PCH     -- use pre-compiled header (experimental, speeds up build)
+If so then we are ready to go!
+Let's clone the repository and start building the i2pd:
+```bash
+git clone https://github.com/PurpleI2P/i2pd.git
+cd i2pd/build
+cmake -DCMAKE_BUILD_TYPE=Release # more options could be passed, see "CMake Options"
+make
+```
+
+After successfull build i2pd could be installed with:
+```bash
+make install
+```
 
 Debian/Ubuntu
 -------------
 
-For building from source on debian system you will need the following "-dev" packages:
-
-* libboost-chrono-dev
-* libboost-date-time-dev
-* libboost-filesystem-dev
-* libboost-program-options-dev
-* libboost-regex-dev
-* libboost-system-dev
-* libboost-thread-dev
-* libssl-dev (e.g. openssl)
-* zlib1g-dev (libssl-dev already depends on it)
-* libminiupnpc-dev (optional, if WITH_UPNP=ON)
+You will need a compiler and other tools that could be installed with `build-essential` package:
+```bash
+sudo apt-get install build-essential
+```
+
+Also you will need a bunch of development libraries:
+```bash
+sudo apt-get install \
+    libboost-chrono-dev \
+    libboost-date-time-dev \
+    libboost-filesystem-dev \
+    libboost-program-options-dev \
+    libboost-regex-dev \
+    libboost-system-dev \
+    libboost-thread-dev \
+    libssl-dev
+```
+
+If you need UPnP support (don't forget to run CMake with `WITH_UPNP=ON`) miniupnpc development library should be installed:
+```bash
+sudo apt-get install libminiupnpc-dev
+```
 
 You may also build deb-package with the following:
-
-    apt-get install build-essential fakeroot devscripts
+```bash
+sudo apt-get install fakeroot devscripts
 cd i2pd
-    debuild --no-tgz-check # building from git repo
+debuild --no-tgz-check
+```
 
 FreeBSD
 -------
@@ -49,17 +63,35 @@ Branch 9.X has gcc v4.2, that knows nothing about required c++11 standart.
 
 Required ports:
 
-* devel/cmake
-* devel/boost-libs
-* lang/gcc47 # or later version
-
-To use newer compiler you should set these variables:
+* `devel/cmake`
+* `devel/boost-libs`
+* `lang/gcc47`(or later version)
 
+To use newer compiler you should set these variables(replace "47" with your actual gcc version):
+```bash
 export CC=/usr/local/bin/gcc47
 export CXX=/usr/local/bin/g++47
-
-Replace "47" with your actual gcc version
+```
 
 Branch 10.X has more reliable clang version, that can finally build i2pd,
-but i still recommend to use gcc, otherwise you will fight it's bugs by
+but I still recommend to use gcc, otherwise you will fight it's bugs by
 your own.
+
+CMake Options
+-------------
+
+Available CMake options(each option has a for of `<key>=<value>`, for more information see `man 1 cmake`):
+
+* `CMAKE_BUILD_TYPE` build profile (Debug/Release)
+* `WITH_BINARY`      build i2pd itself
+* `WITH_LIBRARY`     build libi2pd
+* `WITH_STATIC`      build static versions of library and i2pd binary
+* `WITH_UPNP`        build with UPnP support (requires libupnp)
+* `WITH_AESNI`        build with AES-NI support (ON/OFF)
+* `WITH_HARDENING`   enable hardening features (ON/OFF) (gcc only)
+* `WITH_PCH`         use pre-compiled header (experimental, speeds up build)
+
+Also there is `-L` flag for CMake that could be used to list current cached options:
+```bash
+cmake -L
+```