Implement global state for files with Vuex

With increasing interaction between components it makes sense to have a global state so any component can update and read the global state instead of passing updates up and down the Vue component tree. In particular this is useful so that the current timeline time can be updated from anywhere easily with the changes reflected in all components.

Test: N/A
Change-Id: Ie099973b8a36915c7e93e4d716b0f92e82ab28b4
10 files changed