Capitalize docassemble correctly (i.e., without capitals) throughout

[samglover]

From @jhpyle:

In the documentation I consistently call it docassemble but I sometimes use Docassemble so that people don't think I am e.e. cummings. However DocAssemble is completely and utterly wrong.

Let's use the canonical capitalization throughout.

[nonprofittechy]

Search and replace. I can do this one.