apps/examples/helloxx entry point name was mangled when built as an NSH builtin; plus some README updates

configs/hymini-stm32v converted nsh and nsh2 configs to use kconfig-frontends tools; Also converted to use the common SSD1289 driver

Default NxWidgets and NxWM priorities should be 100 not 50 to be consistent with other default priorities

configs/mikroe-stm32f4:  Add new configurations plus support for the MIO283QT2 display from Ken Pettit

Rearchitecting of some MTD, partition, SMART interfaces, and FLASH drivers to:  Better use the byte write capbility when available and to use smaller erase sectors for the erase sector size when available).

Add support for the byte write method to MTD partition logic;  Beef up the MTD partition test -- and fix resulting bugs detected