Handle the dynamic "STARTUP_*" Histogram names.

For certain histograms, one histogram can be submitted as both X and STARTUP_X
so we now handle these.
Add support for a schema specification

The schema specifies allowed values for each dimension.  Allowed values can
either be specified as "*" to accept any value, or as a JSON array of specific
values to be allowed.  Both cases will be subject to sanitization when being
converted to a filename.
Whitespace and general code cleanup
Ignore a couple more things

Ignore histogram_tools.py, since it's external.
Ignore PyCharm ".idea" directory.