remove HTML from analysis description files

Luckily this didn't require any corresponding changes to the Visomics
source code.
new dynamic parameter type: Column

This commit adds a new type of parameter for our analyses: column.
Instead of manually typing in the name of a table's column, users
can now select from a drop-down list of automatically populated
values.
Merge branch 'populate_analyses'

* populate_analyses:
  new dynamic parameter type: Column
  remove HTML from analysis description files