GUI implemented

TODO: GUI needs work

Adding explanation when sqlite db is not writable

Haanga doesn't support variables starting with 'end' (reported at
https://github.com/crodas/Haanga/issues/14)
Use of {{base.sparqlendpoint.local}} in the meantime

Adding better error report when sqlite is not writeable.

Adding namespace.php including all namespaces available from
http://prefix.cc

Removed functions related to extract  metadata from a SPARQL endpoint,
it stores it on the sqlite database. This will ease the installation
process