data/db: add counting methods for Artists, Albums, Songs, Folders
api/status: add metrics about wavepipe database
API: add documentation about api/status Metrics object
core/apiRouter: add logging of query parameters
api/status: move Metrics to common/metrics
API: fix Metrics object link
core/apiRouter_test: add api/status?metrics=true test
core/cronManager: add metrics to status logging output
Revert "core/cronManager: add metrics to status logging output"

This reverts commit 7dd490db0c4095719f938be864bdca82431d8b07.
data/db_sqlite: fix SearchAlbums() and SearchSongs() queries, adding proper joins
core/apiRouter: add /robots.txt route to disallow crawling
config: change Port to Host for added flexibility
config: fix Travis build
auth: remove unused errors, add new errors, fix panic in basicCredentials()
api/auth/auth_test: initial commit
api/transcode: add missing return
core/apiRouter, api: initial commit of martini -> negroni port
api/art: martini -> negroni
core/apiRouter: re-enable art routes
api/artists: martini -> negroni