small edits to build_db: decimation fraction now a variable
added basic lfp class
basic lfp dataset functionality working
decfrac now takes a simple integer as argument
added support for sampling rate in LFPset
added utility function to fetch lfp in class form
build_db no longer writes sampling rate as metadata
default behavior of bandlimit is now no filtering
added utility functions to LFPset
changed utils to return new dataframe
added method to calculate instantaneous power
added generic metadata dict to LFPset
censoring now works in LFPset
Merge branches 'lfpclass' and 'master'