IMKBilin material updates

1) removal of unnecessary code that was originally intended for smooth transition between loading branches.
2) removal of unnecessary global variables.
3) bug fix for residual strength plateau.
4) bug fix for relatively large strain increments.
5) exchanging several "if" statements with " elseif" statements for efficiency.
6) replacing zero strength and stiffness values with 1.e-6 to avoid convergence issues.

SRC/material/uniaxial/IMKBilin.h

@@ -158,15 +158,7 @@ class IMKBilin : public UniaxialMaterial
 	double Mreversal, cMreversal;
 	double TangentK, cTangentK;
 
-<<<<<<< HEAD
-
-=======
-	double beta_Sx, cbeta_Sx;
-	double slope_p_x, cslope_p_x;
-	double Mpe_x, cMpe_x;
-	double Theta_y_x, cTheta_y_x;
-	double MpeProject_x, cMpeProject_x;
->>>>>>> b6266149a97dc285d766a59024ab57dafc9c1437
+
 };