Mime tools for Notepad++ v3.1 release

1. Add accurate descriptions for all API (messages for sending to Notepad++).
2. Update header files.

e66f7fbae3a2ab23670764ce57265003c520afcf328d6bbf1add195119824199  mimeTools.v3.1.arm64.zip
8df4ef5c94579639f5c429f97e13fe39802552d56db7e7eb3df226ccc9caae9b  mimeTools.v3.1.x64.zip
dd171922d399a4044215554c08e771b0e130c66a288b513802cb7e3d96d94a8f  mimetools.v3.1.zip