code needs clean up and reorganisation

[fwyzard]

• remove default parameter values, unless it really makes sense for such parameters to be optional
• most functions should not accept both a configuration "branch" (e.g. /dev/CMSSW_7_6_0/HLT) and a specific version (e.g. /dev/CMSSW_7_6_0/HLT/V14). A single function should convert a branch to its latest version.
• move all ConfDB v2 code in a single package (e.g. confdb_v2/)
• remove the code duplication between exposed and converter
• remove commented out sections of code