Allow BSP to override scripts with syscfg
Allow BSP to override scripts with syscfg

Before commit, a `bsp.yml` file could not conditionally override its
script names based on syscfg settings.  For example, if a `bsp.yml` file
contains these lines:

    bsp.downloadscript: "my_script.sh"
    bsp.downloadscript.MY_SETTING.OVERWRITE: "your_script.sh"

then `newt load` would always use the "my_script.sh" file, even if
`MY_SETTING` is set to 1.

This commit allows the user to override a BSP's scripts based on syscfg
state.

The fix is to re-parse the BSP package before loading or debugging.

apache/incubator-mynewt-newt,apache/incubator-mynewt-newt