[FIX]Fixed multi currency issues with assets

The branch resolves two issues:
1) When the asset is created in currency other than its company currency, the amount in the depreciation lines get converted to company currency, and when that depreciation line is posted, the amount is again converted in the company currency. Fixed : amount in the depreciation line should be in currency of the asset.

2) On changing the category of the asset, the currency of its journal should be set as the currency of the asset.