Add Erlang analyzer

[trondn]

This patch is a modification of the patches created by
Haitao Li lihaitao@gmail.com back in 2011 and made available
at https://bitbucket.org/liht/opengrok/branch/erlang-analyzer

The OCA is accepted

[lht]

I accept and am OK with OCA for this patch.

[tarzanek]

great, I guess we only miss some junits, but that can be done later ... accepting, since Travis passed
@trondn @lht will one of you be available to write a junit for the analyzer so it's covered?

[tarzanek]

hmm, I accepted an we miss copyrights, ok will add them later
...

[tarzanek]

hmm, one more thing we forgot - add this to SearchHelper.java
into filedescriptions ... will fix with copyright ...

[tarzanek]

see #912

[tarzanek]

alt. I should rewrite in how we generate the filedescriptions - they should come from analyzers, this data should be isolated inside analyzer and not taken from helper class (but helper class should build it from the known analyzer list)