Change study_id retrieval

study_id is now pulled from form if it is not present in sess,
allowing exort_sample_grid.psp to be used in contexts where the
study_id may not be defined in sess.
Remove unused variable study_dir
Add sample summary table function

This is the code that is used to display summary information about samples,
previously only available via study management tools. Because we want to
be able to display this data in other contexts, I wrote this function to
avoid code duplication.
Add function for sample grid display

This is the code that is used to display summary information about samples,
previously only available via study management tools. Because we want to
be able to display this data in other contexts, I wrote this function to
avoid code duplication.
Add message when study has not yet been processed
Change code for study_id lookup
Change select_study_task, use new grid display fn
Merge branch 'master' of https://github.com/qiime/qiime_web_app into show_summary_info
show split_libraries log header, test1
Add another link to download histograms
Add fn to convert tab-delim lines to HTML table
Add fn to generate HTML from split_lib histograms
Add sample grid to study summary page
New page to export split_lib histograms download
Skip blank lines
Add tests for tab_delim_lines_to_table
Add docstring
Add docstring; change open from default mode to U
Add docstring
Change HTML string generation method; change test

Instead of building up the string by successive string concatenations,
instead build up a list and then use string.join to build the final string