Updates for interface labels, visual assets, and code references to consistently reference Peershares

Resolves #67 - General replacement of labels, help text, visual assets and code references to consistently reference Peershares. Changes included: 

* Updated the file names for the daemon and QT clients that are created during a build (peersharesd and Peershares-Qt)
* Remove in application references to "Bitcoin," "PPCoin," "Peercoin," "BTC," and "PPC" (unless being used in the Peershares > Peercoin dividend functionality, in which case it was left alone)
* "PPC" references in the UI have been replaced with "shares"
* "Wallet" references (label only) replaced with "Portfolio"
* Transaction fee text updated to reference that the network fee is mandatory and fixed, based on the size of the transaction.
* Splash screen updated with Peershares logo
* Icons updated
* README.md text updated to appropriately refer to Peershares, instead of Peercoin.
* References in the localized files updated for Peershares

Items that are not covered in this update, but that will be included in a future build tied to different issues:

* Updated build instructions
* Updated Gitian signature instructions
* Final updates to the different language instructions