Changed "usedText" to "usedURL"

In preparation for allowing the user to set an arbitrary “usedText”
string, the profile matched URL is now stored in the ‘alt’ attribute of
the input field.

This frees the usedText value so it can be used just for password
generation.

Other bits of code have been adjusted to use “usedURL” to avoid
confusion.
Add "Use This Text" to options page

Added input field to options page.
Made changes to options save/load function
Added strUseText variable to profile class with getUseText() function
Use profile strUseText for generating password

If strUseText is not null for profile, use that instead of profile
matched url
Merge pull request #66 from stalks/usetext

Allow user to set own text per profile