Don't create log directory in various places

[Akira Sugiura]

Currently, Prig creates log directory in the work directory of the execution program. This causes strange phenomenon. For example, if you execute Visual Studio as normal user from the Start menu, you will get an error like the below when adding Prig assembly:

This is because Prig tries creating the directory in the same location of devenv.exe -- C:\Program Files (x86)\Microsoft Visual Studio 12.0\Common7\IDE.

However, if you execute Visual Studio by clicking a sln file, it doesn't occur. Because the working directory is same as the sln file.

I think that Prig should create log directory in the fixed location that any normal users can write(e.g. %URASANDESU_PRIG_PACKAGE_FOLDER%\tools\log).