genesets route for local server (#2079)

* first cut at GET /genesets route

* update existing tests to match code changes

* more GET /genesets and initial tests

* add missing test fixture

* geneset validation accepts OTA format

* genesets route: better error handling, more tests

* lint

local_server/test/fixtures/pbmc3k-genesets.csv

@@ -0,0 +1,12 @@
+# Test fixture
+geneset_name, geneset_description, gene_symbol, gene_description
+first geneset name,,F5, a gene_description
+first geneset name,a description, NO_SUCH_GENE, non-existent gene
+first geneset name,a description, F5, duplicate gene
+first geneset name, a description, SUMO3,
+first geneset name,, SRM,
+second geneset,,RER1
+second geneset,,SIK1
+third geneset,,NO_SUCH_GENE
+fourth_geneset,fourth description,,gene intentionally missing
+fifth_dataset,,,