Rewrite of battery models in intro and addition of circuit to metho

Added everything except for electrical-circuit models to intro. Analytical models still needs a rewrite.
Methodology has the circuit model and state space equations. Implementation of the filters still needs to be written.
Changed bibliography management system from BibTex to biblatex and using biber for backend. Also using subfiles package after switching to atp from latex-suite.
Removed chapter 3 since it needs changing. Kept in graph in methodology.