GitLab

Added
* Server data check
* Unit tests
* Scripts for easy test setup

Changed
* Integration tests refactored
* Sentinel messages formats

This makes a lot of improvements in build system. The primary change is
that there is now simple bootstrap script that silents autoreconf
warnings by solving them upfront and also covers support for older
Debian.

Rename structure holding Sentinel message data

Previously an empty key, value pair was ignored in case either key or value had zero length.
Now a pair is sent even the value has zero length.
Non-zero length key is still required.

for convinient test setup

for better convinient test setup