[#77716248] replace 'value' with 'balance' where appropriate
[#77716248] replace @total_current_value with Account#children_value
[#77716248] refined 'investment accounts' shared context
[#77716248] created 'savings accounts' shared context in account spec
[#77716248] refactored Account#value, simplified meaning
[#77716248] add Account#value_with_chidlren
[#77716248] add Account#children_cost and #cost_with_children
[#77716248] #gain_loss & #unrealized_gains consolidated to #gains
[#77716248] corrected typo in haml page
[#77716248] added Account#shares and finished updating holdings page
[#77716248] rerouted holdings to accounts controller
[#77716248] removed holdings controller
[#77716248] removed Holding and HoldingCollection classes