Added to schema parser the ability to evaluate simple comparison
expressions in the form (@{attribute} [operator] "value"). This will
facilitate the creation of conditional SQL code based on
PostgreSQL versions.
Improvements on all schema files that makes use of @{pgsql9x} attribute.
Those attributes were deprecated and replaced by comparison expressions.

The method SchemaParser::storePgSQLVersion was removed due to the
deprecation of attribute @{pgsql9x}.
Merge branch 'sch-parser-improvements' into model-db-sync
Creatd own versions of getDropDefinition for Function and Index

Model db diff feature checkpoint. The resultant diff now is saved to
output file.