Add static library note to linux section.

- Some Linux users might skip the Windows build section and thus miss the note about the static libraries.  Therefore, copy the note about the static libraries to the Linux build section.
Remove Linux part of note from Windows section.

- Now that the Linux section contains a note about the generated static libraries, in the Windows section the part of the note, about which libraries are generated under Linux, is redundant.  Therefore, remove it.
Copy where to find static libraries to linux section.

- Forgot to copy this part of the note in commit #6abffd6.
Make install and using cpp-netlib.

- Add make install command
- Add section about how to use cpp-netlib from a CMakeLists.txt.