Remove kachery storage check, fix name splitting, fix sample rate calc

[rly]

1. Remove check to see if $KACHERY_STORAGE_DIR exists and is consistent with SPYGLASS_BASE_DIR.
2. Names with three space-separated items could not be inserted into spyglass because this code:

   labmember_dict['first_name'] = str.split(full_name)[:-1]

   returned an array of strings instead of a string. Here we join those strings with spaces into a single string. This is a stopgap solution until LabMemberInfo should not ask for full_name #304 is resolved.
3. Fix the sample rate calculation when timestamps are not provided.
4. Do not import the data_import module when importing spyglass, so that datajoint and mysql are not triggered when loading any spyglass.* module
   • Eventually the processing parts of spyglass will be separated from fetch/insert calls so that they can be tested independently of the database (not yet implemented).
5. Remove old and no-longer-needed backup spike sorting keys