Factored tsv code, added REST API for selections;

Added REST API for LIMMA as follows:

1) curl -b cookies -c cookies -F "dataset[]=@test.data"
http://localhost:8080/dataset?format=tsv
2) curl -X PUT -b cookies -c cookies -d "keys=sb" -d "keys=sa"
http://localhost:8080/dataset/test.data/column/selection/sel1
3) curl -X PUT -b cookies -c cookies -d "keys=sc" -d "keys=sd"
http://localhost:8080/dataset/test.data/column/selection/sel2
4) curl -b cookies -c cookies -X POST
"http://localhost:8080/dataset/test.data/analyze/limma/myLimma(dimension=column,experiment=sel1,control=sel2,alpha=0.2)"
5) curl -b cookies -c cookies
"http://localhost:8080/dataset/test.data/analysis/myLimma?format=json"
Merge pull request #430 from lev-kuznetsov/master

Factored tsv code, added REST API for selections;