add support for aggregations to find() and count() mongo operations
add support for aggregations to CM_PagingSource_MongoDb to allow more complex search operations
ci: install mongo server 2.6.x
use 'skip' and 'limit' operations for offset and count instead of unavailable cursor->skip() and limit() operations when using aggregation
jsonEncode mongo call-params for debug info
add more info to individual debug usages
add aggregation-capabilities to CM_Service_MongoDb::findOne()
add test for findOne()
implement createCollection(), createIndex(), hasIndex(), dropDatabase() on CMService_MongoDb
clean up mongo collections after each test
Merge branch 'master' of github.com:cargomedia/CM into MongoDb-adjustments
Merge branch 'master' of github.com:cargomedia/CM into MongoDb-adjustments
add sorting capabilities to CM_PagingSource_MongoDb
take field-order into account when checking for existence of compound indexes
take index-direction (ascending, descending)  into account when checking for index-existence
minor simplification (use some() instead of !none())
remove manual instalation of mongo 2.6
remove debug var_dump()
ci debug
Revert "remove manual instalation of mongo 2.6"

This reverts commit 15bbbbfef190cd8329903689e275af9ea2932967.

Conflicts:
	.travis.yml
use non-strict comparison for index-direction to avoid index-direction type mismatch problems (int vs double)
Merge branch 'master' of github.com:cargomedia/CM into MongoDb-adjustments

Conflicts:
	library/CM/Service/MongoDb.php
	tests/library/CM/Service/MongoDbTest.php
revert accidental commit