Added 'Locator Should Match X Times' keyword similar and more generic version of 'Xpath Should Match X Times' keyword and test.
Moved 'Locator Should Match X Times' acceptance test.

Moved test from test/acceptance/keywords/elements.txt to
test/acceptance/keywords/content_assertions.txt.
Merge pull request #298 from emanlove/locator-x-times

Added new keyword 'Locator Should Match X Times'