Add Path support to TextFile.

Change-Id: I752f5bebe42514f1dc21e1b77e1ee5a649f324f5
Depends-On: I9463e66dc39881bcc69b64b8900df1010683b0bc
Depends-On: I752f5bebe42514f1dc21e1b77e1ee5a649f324f5
Depends-On: I4fa54ebe8f4ff93c8fc33504af66338eda01d0b8
Reviewed-on: http://gerrit.dmdirc.com/3502
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Chris Smith <chris@dmdirc.com>