Style refactor all .cpp filenames + adjust license formatting for clang-format

[anonimal]

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1. To keep in order with our upstream guide, we should rename all files from .cpp to .cc and change from MixedCase.cpp to single_case_with_underscore.cc. Once that's done, remove the line about filename style in our style guide.
2. Because our column limit for clang-format is 80, clang-format will squish the license in formatted files. To avoid this, we need to amend a // at the end of each line like so:

/**                                                                                       //
 * Copyright (c) 2015-2016, The Kovri I2P Router Project                                  //
 *                                                                                        //
 * All rights reserved.                                                                   //
 *                                                                                        //
 * Redistribution and use in source and binary forms, with or without modification, are   //
 * permitted provided that the following conditions are met:                              //
 *                                                                                        //
 * 1. Redistributions of source code must retain the above copyright notice, this list of //
 *    conditions and the following disclaimer.                                            //

or, amend clang-format on clang-format off before and after the license which I think is uglier and intrusive. I propose we stick with the less-intrusive version of //. If there is a better way to accomplish 2., I'm all ears.

Referencing #279 and #238.

[anonimal]

Unassigned myself. guzzi jones said he'd take the issue.

[EinMByte]

Let's stick with appending //.
Use of .cc is somewhat less common, but I'm fine with it. Lowercase/underscore has the advantage of avoiding compilation errors (as we've had) on case insensitive file systems, but is a bit less intuitive IMHO. That said, I don't really mind the change (these are not important matters anyway).

[anonimal]

Well, it all adds up (many smaller 'not important' matters turn into large important matter) so I'm glad this is being taken care of. 👍 on the case insensitivity solution; we can resolve that NetDb filename issue once this is resolved.

[anonimal]

Resolved with #299 and #302.

Thanks @guzzijones.

[anonimal]

@EinMByte JFTR: Boost (tested on 1.60) is still problematic with netdb.h and will fail to compile on Arch Linux x86_64 - even with include guard in place (see also /usr/include/netdb.h).

For now, we'll keep net_db.h to complement net_db_requests.h but I would like to see how this conflict can be resolved (or if it has been resolved).