Restore useful comments

[pausz]

Some comments found in EEG code do not longer exist in the current version, making the code more cryptic for a new dev and for anyone reading the code for the first time.

And example of this are the comments found in waveeqn.cpp that never made into wave.cpp.

While most of the development here follows a Solo Virtuoso patter, that is not a license to hack or erase details of previous versions. In particular when a) the revision history of the code has not been ported from svn to git and b) the decisions made when refactoring eegcode into neurofield were not written down.