Change study_id to preprocessed_data_id in ebi
Remove support for multiple preps from ebi

We will be doing a separate EBISubmission for each preprocessed data,
so the object need only support a single prep at a time
Fix tests to expect only one prep
Merge branch 'master' of https://github.com/biocore/qiita into ebi_one_prep_template_per_submission

Conflicts:
	qiita_ware/test/test_ebi.py
New interface for EBI submission command

Has many fewer parameters now since it depends on having a preprocessed data
ID in the database
Add a samples parameter to MetadataMap.to_file

Defaults to None. If it is not None, only the specified samples will be written
to the file.
Roll together dispatchable EBI submit into CLI cmd

The code executed by invoking the CLI call now does almost the same exact thing
as the code executed when invoking the command through the web interface
Merge branch 'master' of https://github.com/biocore/qiita into ebi_one_prep_template_per_submission
Test for new MetadataTemplate.to_file parameter
Add preprocessed data id to study description page

Easier than looking it up all the time
Remove unused param, reorder params
Sample and prep templates must be files, not objs
Default fast_dir to None
Cosmetic fixes to ebi.py
Remove unused imports
Merge pull request #612 from adamrp/ebi_one_prep_template_per_submission

Change EBISubmission Object to Use Only One Prep