Fixing typo.
Merge pull request #24 from Batmat/fix-typo

Fixing typo.
SONAR-4137 fix size of MySQL index of PROPERTIES.PROP_KEY
SONAR-4137 fix varchar indices on mysql 5.6
Fix backward-compatibility. File system can be changed by sensors...
Fix inclusions by absolute path and improve documentation
SONAR-4138 Do not delete manual metrics, just deactivate them

=> Deleting a manual metric should lead to deactivate the metric in 
   the Sonar DB and not to fully drop it
SONAR-4138 Warn user if deactivated metric exists in DB

=> If a user tries to create a metric with a name already used by a 
   deactivated metric.