Added check for duplicate project paths when using pcreate

I created this pull request to fix issue #1225. This patch simply checks for the existence of the project path and then if the project path already exists the program asks the user to choose another name.

I have another branch that does the same thing except asks the user for input if they would like to overwrite the project directory, but I could not figure out how to test user input in the unit tests. If that method is preferable I would be happy to work on that branch if somebody could help me write the appropriate unit test to go along with it. 6edbd2cfde272a108f90e82355ecc0f0005cc6bc