Added four join-functions that join multiple sets or lists

Each function can take an arbitrary number of xrel (lists or sets)
- inner-join
- left-outer
- right-outer
- full-outer
Small fixes to vExcel and vRelation
Small fixes to the error-reporting
Added write-as-rows to vSql
Improved vExcel (reading excel routines)
Small fixes
Added extract-recs

This function can be used to extract a sequence of records from a
join-set again.
Patch for vCsv (failed on keyword keys)
Added (vParams/get-options opts defaults)
Merge branch 'master' of https://github.com/cvkem/vinzi.tools

Conflicts:
	vinzi.tools/src/main/clojure/vinzi/tools/vRelation.clj
	vinzi.tools/src/test/clojure/vinzi/tools/test/vRelation.clj