New parameter '$install_dev' to install development headers.

- Works for Debian and RedHat
- Added new parameter to READEME.md
Merge pull request #19 from tPl0ch/feature/dev-libs

New parameter '$install_dev' to install development headers.
Version 2.1.0
Implement Override  the  default size of each slab page
Merge pull request #20 from zylon-internet/master

Implement Override the default size of each slab page