Move out BandedMatrices code #518

Job	Run time
pre_job	7s
pre_job	7s
pre_job	7s
Julia 1 - ubuntu-latest - x64 - pull_request	25s
Julia 1 - ubuntu-latest - x64 - pull_request	20s
Julia 1 - ubuntu-latest - x64 - pull_request	8m 22s
Julia 1 - macOS-latest - x64 - pull_request	59s
Julia 1 - macOS-latest - x64 - pull_request	50s
Julia 1 - macOS-latest - x64 - pull_request	8m 23s
Julia 1 - windows-latest - x64 - pull_request	39s
Julia 1 - windows-latest - x64 - pull_request	41s
Julia 1 - windows-latest - x64 - pull_request	9m 2s
Julia lts - ubuntu-latest - x64 - pull_request	16s
Julia lts - ubuntu-latest - x64 - pull_request	15s
Julia lts - ubuntu-latest - x64 - pull_request	6m 0s
Julia lts - macOS-latest - x64 - pull_request	42s
Julia lts - macOS-latest - x64 - pull_request	44s
Julia lts - macOS-latest - x64 - pull_request	6m 3s
Julia lts - windows-latest - x64 - pull_request	32s
Julia lts - windows-latest - x64 - pull_request	42s
Julia lts - windows-latest - x64 - pull_request	7m 8s
	52m 24s

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