refactor step 2 - I2C

DAC renamed to I2C
squeezelite thread stack correction
had to move .bss to dram0 (need to verify consequences)

main/output_bt.c

@@ -1,3 +1,24 @@
+/* 
+ *  Squeezelite for esp32
+ *
+ *  (c) Sebastien 2019
+ *      Philippe G. 2019, philippe_44@outlook.com
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+ 
 #include "squeezelite.h"
 #include "perf_trace.h"