Add NoBloating approximation model

[mforets]

Closes #208.

[mforets]

Example:

using Revise, ReachabilityAnalysis, Plots

include("/home/mforets/.julia/dev/ReachabilityAnalysis/test/models/linear/linear5D.jl")

# homogeneous case
prob, _ = linear5D_homog()

sol = solve(prob, T=5.0, alg=GLGM06(δ=1e-2));
plot(sol, vars=(0, 1), lw=0.0, color=:lightblue, alpha=.8, lab="Forward bloating")

sol = solve(prob, T=5.0, alg=GLGM06(δ=1e-2, approx_model=NoBloating()));
plot!(sol, vars=(0, 1), lw=0.0, color=:red, alpha=.8, lab="No bloating")

# inhomogeneous case
prob, _ = linear5D()

sol = solve(prob, T=5.0, alg=GLGM06(δ=1e-2));
plot(sol, vars=(0, 1), lw=0.0, color=:lightblue, alpha=.8, lab="Forward bloating")

sol = solve(prob, T=5.0, alg=GLGM06(δ=1e-2, approx_model=NoBloating()));
plot!(sol, vars=(0, 1), lw=0.0, color=:red, alpha=.8, lab="No bloating")