Client enhancements to get crtime, file magic, and PE headers data

I used MSYS2 with MINGW to build libgnurx-0.dll and magic1.dll for Windows to be able to properly use python-magic.  The installer would also need to be modified to include the file magic database magic.mgc in the client installed directory.

I removed some packing detection and checksum comparison due to it having a pretty significant performance hit on larger binaries.  It may be worth it to enable those via options when a flow is run.

This also carves off the PKCS7 certs on PE files and returns them.  There might be better ways to do this.
Not really.  The Cybox stuff here https://cybox.mitre.org/language/version2.1/xsddocs/objects/File_Object.html doesn't capture nearly as much information about a PEFile.  This is actually more in line with how PE Files are described in the MIR context of OpenIOC.  For GRR I will be setting up the GRR OpenIOC context to use all the various rdfvalue terms for matching.