Allow BridgeRest server config to specify any idmapper, not just idmapper-pgdb

[martijn]

This is a configuration issue. The config file for BridgeRest? requires you to list the file locations of pgdb files that contain mappings. But there is no reason to restrict ourselves to just pgdb files. Using the power of connection strings, we can use any type of idmapper by just putting the protocol in front of it.

The advantage of this would be that we could configure text files for added flexibility, or mysql datbases for added performance. We could even refer back to the webservice itself and create a black hole to destroy the universe.

So instead of

Homo sapiens	/home/martijn/PathVisio-Data/gene databases/Hs_Derby_20090509.pgdb
Mus musculus	/home/martijn/PathVisio-Data/gene databases/Mm_Derby_20081119.pgdb

We want this:

Homo sapiens	idmapper-pgdb:/home/martijn/PathVisio-Data/gene databases/Hs_Derby_20090509.pgdb
Mus musculus	idmapper-pgdb:/home/martijn/PathVisio-Data/gene databases/Mm_Derby_20081119.pgdb
NuGO Custom array	idmapper-text:http://svn.bigcat.unimaas.nl/bridgedb/trunk/test-data/Nugo-hs-custom.txt
MySQL database	idmapper-jdbc:mysql:bigtable

and it should just work as expected.