Rename copyData -> syncData and ensure correct flags set when syncing

[pelesh]

There are two issues addressed here:

• Make wholesale name change copyData -> syncData. Methods syncData synchronize data between the host and device within the same vector or matrix object. "Copy" often suggests data is copied from/to another object. Resolves Consider renaming matrix::Sparse::copyData to matrix::Sparse::SyncData #187.
• The "update" methods copy matrix or vector data to/from external sources and set flags indicating which memory space within the object is up-to-date. For example, if the host memory is updated, host flag h_data_updated_ is set to true and device flag d_data_updated_ is set to false. A sync method needs to be used if one wants to update both. Resolves When only host is updated, the device is out of date (and vice versa) #126.

Both, sync and update methods need to check if the operations are meaningful. For example if syncing device memory space, the host needs to be up-to-date.

[pelesh]

Resolves #188.