trying to create namedprops backend layer

Now it's with data hardcoded and untested
rename namedprops_backend to namedprops_context
by default use ldb file on the usual path
keep it c89 standard
look for mapistore:nprops_backend from smb.cnf to configure mapistore_namedprops
add sql schema for named_properties
add transaction start/commit to named_props backend
move mapistore_namedprops_get_ldif_path to common header

This function will be used for all implemented backends because
they need that file to populate their database
move mapistore_namedprops_get_ldif_path implementation out from the header to mapistore_namedprops.c
initial sketch namedprops mysql backend

99% Not implemented
start and commit trasaction
add named properties sql schema to makefile install section
add "IF NOT EXISTS" on create table statement
namedprops mysql init almost done
new test directory with unittest of openchange code

  * Now it only has unittest for namedprops_mysql.c from libmapistore
  * It uses check framework and cmake for building.
  * It requires to have openchange already installed locally
use markdown for readme file
markdown format
initialize mysql with entries from ldif file
add coverage flags and xml test output
more logic on mysql_connect