NetStandard 1.1+ support, new IdGen.Configuration package, bugfix

Changes:

• Support for NetStandard 1.1+
• Moved AppConfig stuff to separate IDGen.Configuration package
• ID now implements IEquatable
• Fixed some ArgumentOutOfRangeExceptions from the IdGenerator's ctor messages
• Fixed bug (see #18) where internal timer was started only on first use instead of on instantiation. Thanks @stuart-beattie!
• Minor internal cleanup / refactoring

Breaking changes:

If you're using the IdGenerator.GetFromConfig(...) method make sure you check the README. The changes aren't big, but breaking nonetheless. How to fix:

• Install IdGen.Configuration package
• Change the configsection type from:
  IdGen.Configuration.IdGeneratorsSection, IdGen
  to:
  IdGen.Configuration.IdGeneratorsSection, IdGen.Configuration
• Add a using IdGen.Configuration
• Change IdGenerator.GetFromConfig(...) to AppConfigFactory.GetFromConfig(...)

Minor changes

• Added FromId() method to 'decode' an Id
• Minor internal refactoring

Flexible 'ticks'

Timesource(s) is (are) no longer fixed to 'millisecond resolution'; we now have the concept of a 'tick'. Each timesource can define it's own definition of what a 'tick' is, be it a millisecond or a minute or any other timespan.

This means breaking changes in the ITimeSource interface and the way timesources are implemented and breaking changes in some of the MaskConfig's method signatures.

The IIdGenerator<T> interface now explicitly exposes an IdGenerator's ITimeSource, MaskConfig and Epoch as (read-only) properties.

CreateMachineSpecificGenerator() & CreateThreadSpecificGenerator() methods have been removed; these are way to 'dangerous' to use anyway since they are very prone to 'collisions' in 'auto-generated' values for the IdGenerators.

Improved DefaultTimeSource

Moved away from DateTime.UtcNow and implemented a better, millisecond resolution, DefaultTimeSource using QueryPerformanceCounter.

Initial release

* Created documentation welcome page

* 1.0.0 release