Delete destination app dir when preparing project
Delete destination app dir when preparing project

Delete dir where app will be copied on prepare. If we do not delete it, on Linux and Mac we receive EEXIST errors for symlinks inside app directory. Symlinks are common scenario when node_modules are used.

Fixes https://github.com/NativeScript/nativescript-cli/issues/394

NathanaelA/nativescript-cli,jbristowe/nativescript-cli,NativeScript/nativescript-cli,NativeScript/nativescript-cli,NativeScript/nativescript-cli,jbristowe/nativescript-cli,e2l3n/nativescript-cli,lokilandon/nativescript-cli,NathanaelA/nativescript-cli,tsvetie/nativescript-cli,NativeScript/nativescript-cli,NathanaelA/nativescript-cli,jbristowe/nativescript-cli,tsvetie/nativescript-cli,e2l3n/nativescript-cli,tsvetie/nativescript-cli,e2l3n/nativescript-cli,NathanaelA/nativescript-cli,tsvetie/nativescript-cli,lokilandon/nativescript-cli,tsvetie/nativescript-cli,lokilandon/nativescript-cli