Some minor changes

Now possible to control the link command via LINK variable
New variable C_UNDEF which can be used for undef of standard defines
Added libncurses5* in install script
New board minew_E7
Added new function enrf_acm_connected which can be used to check if
  usb-uart is connected
Now possible to let enrfscan show all advertisements from a match

Bug-fix in enrf_delay_ms

Added enrf_delay_ms

Fix bootloader error introduced in previous commit

The correct variables were no exported during bootloader generation
  leading to key error for dfu operations. Now corrected.

Updated functionality

New board Invector connectivity_nrf52_lte
Now possible to disable both bootloader and softdevice for plain applications
  New example added which show this
Some astyle syntax updates
New variable BUILD_VERSION_HEADER for possible prefixing of the version string

Some additional features

BOARDS_DIR now exported for bootloader build
New variables:
  COMP_DEP_EXTRA Adds extra dependencies to to compile operations.
  BUILD_VERSION_TAIL Adds extra tail string to the automatically
                     generated version information.

Make bootloader dir configurable

Minor fix for vscode file generation

Some VS code improvements

Improved flash operations

Better and more consistent handling of flashing operations.
Adjustment for latest bleak version.