Changed tolerance check and added bracket check.

Added a check ensuring a root is bracketed - that is, the function
changes sign between the lower and upper bound. Also changed convergence
check to be consistent with a relative tolerance.
RootFinding: auto zero-crossing bracketing expansion in FindRoots.OfFunction; include missing R# settings, apply
Distributions: increase Brent root-finder accuracy in Beta, F and Student-T inverse CDF to adapt to fixed Brent behavior
Build: fix paths to improve support for Paket
Build: paket install
Build: for F# on net35 use traditional FSharp.Core reference instead of NuGet

For C# and also for all non-net35 F# targets we still use the proper NuGet package.
This allows us to use one FSharp.Core NuGet package only (instead of two
with platform-groups), resolving quite a few issues.
Release v3.3.0
Release notes typo
Build: paket reinstall