Advanced file search

[Moneyl]

Add advanced search options that use information read from the RFG file headers. Not sure if this should be put in the file explorer or a new form. Ideas:

• Search for textures used by meshes or effect files. With option to tell you which peg/vbm file to find them.
• Search other strings in files (including strings sourced from hashes), such as shader names, material constants, etc.
• Search properties values and object names/handles of objects in rfgzone_pc and layer_pc files.